1. Technical Field
The present invention relates to a test apparatus.
2. Related Art
When testing a device under test such as a semiconductor circuit, the power supply apparatus that supplies a power supply current to the device under test sometimes cannot quickly follow fluctuation in the current consumed by the device under test. One known technique for solving this problem involves providing a bypass capacitor in a power supply line near the device under test, as shown in Patent Document 1.
Patent Document 1: Japanese Patent Application Publication No. 2001-195139
Patent Document 2: U.S. Pat. No. 6,087,843
When there is a large fluctuation in the power supply current, a bypass capacitor with a high capacitance, such as tens of μF, is provided to track the fluctuation. A small output current of the power supply apparatus can be measured to measure a small current such as a standby current. In such a case, the load capacitance connected to the power supply apparatus is limited, and so a reed relay is provided to disconnect the high-capacitance bypass capacitor from the power supply line.
However, the reed relay cannot be provided because there are structural restrictions near the device under test. Therefore, the high-capacitance bypass capacitor must be provided at a distance from the device under test.
As a result, the power supply line from the bypass capacitor to the device under test is lengthened, and so the inductance component between the bypass capacitor and the device under test increases. This makes it difficult to supply high-frequency current from the bypass capacitor to the device under test.
One type of test for the device under test involves measuring the power consumed during operation of the device under test. With this test, the power consumed by the device under test is measured by measuring the current flowing through the power supply line. More specifically, the power consumed by the device under test is measured by measuring the current flowing through the power supply line closer to the device under test than the bypass capacitor.
As described above, however, it is difficult to supply a high-frequency current from the high-capacitance bypass capacitor to the device under test. Therefore, even if the current flowing through the power supply line is measured between the high-capacitance bypass capacitor and the device under test, it is difficult to accurately measure the consumed current of the device under test which fluctuates at a high frequency.